A mobile communication unit may comprise a modem (modulator/demodulator) unit, which encodes information and modulates a signal to be transmitted, and also demodulates a received signal and decodes information contained therein. By use of a modem unit a signal is produced that can be transmitted easily and a received signal can be decoded to reproduce the original information. Modems can be implemented not only in mobile communication units but also in other communication units like stationary communication units, data processing units, personal computers or the like. Modem units can comprise memory units like volatile and non-volatile memories for storing different kinds of information or data therein.